Arvind Narayanan's journal

Considering the huge role that caffeine can play in enhancing (workplace)
productivity, it is worthwhile to study its effects and mechanism with the hope
of maximizing this productivity-enhancing effect. I've done the legwork for
you, so sit back and read. The results might surprise you.Mechanism. Caffeine has a number of
effects on the body, but the one that is relevant here is that it blocks
adenosine receptors in the brain (by tricking your brain into thinking it is
adenosine.) A decrease in the activity of adenosine (which is a sleep
chemical) increases neuron firing rate and increases focus and concentration.

Caffeine tolerance builds up rather quickly (2-3 weeks) and further, is
near-total. That means that if you drink coffee regularly, pretty soon you
start producing more adenosine in respose; thus you need your caffeine dose
just to get up to your normal level of brain activity, and you're dopey if you
don't take it. Another way to think about it is that the time-average of
adenosine level (and hence, attention level) tends to stay more-or-less
constant, both short term and long term.

Short term strategy. Let us examine
the way that most people take caffeine -- when they feel sleepy (I will call
this antagonistic consumption.) This
changes the attention level from the green line to the blue line (i.e, it
smooths out the fluctuations.) This works great for many people (say,
someone that has a data entry job), because maximum productivity is limited
by external constraints. Other jobs where antagonistic consumption is
essential include assembly line worker and truck driver, where mistakes can
be disastrous but there is little to be gained from peak concentration.

Daily fluctuation in attention level, highly oversimplified. The
green line represents no coffee. The blue line is antagonistic
consumption. The red line is reinforcing consumption.

But other jobs, often characterized by a low level of repetition, have a
markedly different attention-productivity curve. Academic research, for
instance, involves generating ideas that no one has come up with before.
Clearly, an idea that advances the state of the art is unlikely to occur
except when attention level peaks. If you spend your entire day doing
nothing, but all that doing nothing somehow enables you to reach a point
where you understand your research problem well enough that you get insights
that no one ever did before, then that's good research. Writers are another
example: it is common to sit around for days or weeks waiting for
inspiration to hit ("writer's block").

What is common to these tasks is that progress happens in spurts, due to the
fact that they involve frequent
cognitive
bottlenecks. A cognitive bottleneck can only be overcome when
attention level exceeds a task dependent, typically very high threshold.
Clearly, then, antagonistic caffeine
consumption results in worse-than-normal productivity, because it
flattens the attention level curve and decreases the fraction of time spent
at peak attention level. Instead,
reinforcing consumption helps
maximize productivity (the red line). According to this strategy,
the best time to drink coffee is when you are
already very alert.

Productivity as a function of attention level for naturally
rate-limited tasks (green line) and tasks with cognitive bottlenecks
(blue line). The former is
concave and the latter is
convex.

A job like driving trucks is one end of the spectrum, where productivity is
naturally and insuperably rate-limited. Jobs with frequent cognitive
bottlenecks like at the other end. In each of these cases, the optimal pattern
of caffeine consumption is clear. Most other jobs fall somewhere in between,
and each person must make a reasoned decision about what works best for
them.

Sleep. The reinforcement strategy has
another element to it. When adenosine peaks, the best response is not to fight it,
but "go with the flow" and (shock, gasp) sleep. Sleep has effects on
memory consolidation and is extremely beneficial in overcoming cognitive
bottlenecks, making the brain maximally alert right after waking up. Thus, a
possibly very effective coffee drinking pattern would be two cups a day, one
early in the morning and one right after an afternoon nap. (Unfortunately,
napping is stigmatized in the Western work culture, despite much scientific
evidence touting the benefits. I hear that such stigmatization is non-existent
in China. Good for them.)

Long term strategy. Over the long term,
consistent caffeine consumption is as good as nonconsumption, because of (you
guessed it) tolerance. Is there a better strategy? Of course there is.
Periodic abstinence lets adenosine levels return to normal. With complete
abstinence, it takes 5 days to reach adenosine normality; conservatively, and
with imperfect abstinence, a week or 10 days may be required. (Quitting is
hard!) For most people, work involves a natural cyclic pattern of crunches and
lean periods, and moderated coffee consumption to reflect this pattern
will let you enjoy its cognition-enhancing effects more-or-less permanently.

Notes.

1. Many products contain caffeine, especially sodas. Carelessness about
extraneous caffeine sources will diminish the effect that well-planned
coffee-drinking can have. (Of course, the sugar in sodas is far more harmful
than the caffeine, so that would probably be the least of your worries.)

2. Personally, since I discovered these principles 6-8 months ago, I've had an
absolutely unbelievable time in terms of research productivity. I've also had
3-4 quitting cycles in this time period (which is less than ideal, but I
didn't realize the importance of quitting until later.)

3. There appears to be a generally low awareness of cognition-enhancing
substances in general, such as
creatine.
I plan to expand on this in a later essay.

4. This essay (and everything else I write on this blog, unless otherwise
stated), is licensed under
CC-by-SA.

"If I took a nap when I was sleepy enough to fall asleep during the day, I wouldn't ever get anything done. I'm always tired enough to take a nap."

Well, have you ever given it a try? A half hour nap can leave you refreshed for the rest of the day.

"What is the half-life of caffeine in the body?"

By which you demonstrate that you know that caffeine decays by first-order kinetics :) Anyway, the half life is apparently highly person-dependent. 3-4 hours for the majority of people.

"I thought creatine is marketed as a muscle-repairing (?) thing? I've known a couple body builders who take it regularly."

And that's why I started taking it too. And therein lies the tragedy -- very clear memory-enhancing effects have been demonstrated, yet no on is aware. Anyway, let me not start on that now, I feel strongly enough about it that I'm definitely going to write about it in the future.

A half-hour nap makes me feel more sleepy than if I don't nap at all. I tend to require 9-10 hours of sleep a day in order to function.

I don't like coffee because it tastes icky and it colors your teeth. Over the last month, I've taken a few caffeine pills to help with thesis productivity. It's helped greatly. Of course, I worry about that whole tolerance/dependence issue. The caffeine pills I have contain 200mg. I do wonder if taking 100mg. at one time and then another 100mg. X hours later would be more effective than taking 200mg. at the start.

good stuff

A very well written essay my man. Kudos! Have been following your blog, quietly though, for sometime now.

The things about all those chemicals ending in an 'ine', bbc-science has good write ups about. Looking forward to your essay on creatine and the effects of exercising on cognition/attention-span/general brain power.

Ofcourse in dear old India its another thing if I actually find things like creatine supplements here and if they are, are they affordable on a regular basis. Hmm. Is creatine naturally occurring, like in some food..? Got to find out.

That was a really interesting read. I am almost entirely caffeine-free now (I just prefer not to use stimulants after quitting coffee in college. . .) but this took me back to my heavily-caffeinated days!

That was a really interesting read. I am almost entirely caffeine-free now (I just prefer not to use stimulants after quitting coffee in college. . .) but this took me back to my heavily-caffeinated days!

More justification for your blue line?

I love your result, but there's one thing you need to provide a bit more evidence for.

You suggest that caffeine enhances attention level, but (in the case of the blue line) you suggest that the antagonistic consumption of caffeine tends to lower the attention level in the ordinarily attentive parts of the cycle. However, you don't provide evidence for this. You suggest that your body compensates for the blockage of adenosine over a period of 2-3 weeks, but this profile suggests that this compensation occurs even in the 2-3 *hour* time frame.

I'm perfectly willing to believe that this is the case, but you don't actually make this claim directly. Is this in fact the case?

Re: More justification for your blue line?

oh, that's a slightly different phenomenon. caffeine has a half life in the body (which is extremely well-documented.) since caffeine blocks adenosine receptors, the adenosine waits until the caffeine is gone, and rushes in all at once. (oversimplified :-)

so it's not that you start to produce more adenosine, but rather, the adenosine that's there binds to the receptors all at once, causing the "crash" that we're all familiar with.

coffee often has opposite effect

I often have the reverse effect - I drink coffee, get a little burst of energy and a few mins later fall off the curve and become sleepy. I don't think my body can metabolize caffeine that quickly. Is it possible that the body compensates for regular less sleep than needed and excess coffee consumption by generating more adenosine and so quickly?

Re: coffee often has opposite effect

I'm with you on that. I often find myself waking a couple hours early in the morning, then just giving up on sleep. I go have a cup of coffee and before you know it, I'm back in bed, making up those two lost hours of sleep.

Re: coffee often has opposite effect

Yes I experience this effect too - but I feel it is to do with not having enough caffeine in ones system to make it through the night before mild withdrawal symptoms set in. You wake up early feeling a little uncomfortable because of these withdrawal symptoms, have a cup of tea feel better and then go right back to sleep. I only started to get this when I started to try to cut down on my caffeine during the day. Plotting the subjective effects of various common intoxicants is quite interesting. Thomas DeQuincy (Confessions of an English Opium Eater) speculates that the pleasure induced by drinking alcohol is 'acute' and always tending to a peak before it rapidly fades away, but opium induces a 'chronic pleasure lasting 12 hours for example. Suely there is an optimum strategy for alcohol consumption too?

My coffee experience is weird

I drink about 10 cups of coffee per day (espresso). Even if I drink one shortly before I go to bed, it has no impact,...I fall asleep within minutes...On holidays, I usually drink NO coffee at all and I dont miss it. When I am back at work I just have the DESIRE to drink coffee.My scenario made sense if I think about the (needed) level of concentration which is not necessary on holidays, but then, why do I have the same DESIRE for coffee at home on weekends?P.S. I can drink 3 red bulls in sequence and still be able to sleep...

I think your article on Caffeine is great. That's why I am confused by your stance on sugar. Your the first person I've found who really seems to understand caffeine (I did my grad work in psychology in the neuroscience department at Baylor U. where I learned a lot about caffeine). Everything I learn about table sugar from scientific sources seems to point to it as a relatively low GI food (65 on average) relative to things like potatos and white bread. Since every form of food eventually gets turned into sugar, I don't see what the problem is as long as you make up for the deficiency of vitamins and minerals with suplements and other green/colorful foods.

I've always thought that all the anti-sugar stuff was a bunch of moms with nothing better to do or nutritional experts trying to scare people into buying their consultation services. But since I respect your scientific scrutiny on the issue of caffeine, I'd like to ask you a question.

Why would a high table sugar diet be worse than a high white-potato diet if you took a supplement that made up for the missing potassium and fiber that is found in potatoes? Since potatos have a high Glycemic index and that has been associated with diabetes and heart disease, I'm thinking a Snicker's bar or peanut M&M's (both extremely low GI) are one of the healthiest foods for a person to eat if you add some fiber and vitamins/minerals from other sources.

I'm not sure that the two diets are terribly different. The research I've done on sugars definitely points to problems with, say, a high-potato diet.

The confounding thing is that the quality of carbohydrates matters as much as which ones: how they're prepared, what they're eaten with. In the American Journal of Clinical Nutrition's lated glycemic index table, there's variation between glycemic index (compared against pure glucose) of 50 points between glucose alone and glucose fed with oat fiber. (Am J Clin Nutr Foster-Powell et al. 76 (1): 5.)

There are definite interlinks between serotonin receptors (which can affect depression and various other mental states) and carbohydrate digestion. A lot of these things play together.

I know from personal experience that I suffer less eating potatoes than sugar -- but I never eat just potatoes. They're always fried, mixed with meat, or with other vegetables. Sugars, when I eat them, tend to be mixed with white flour or made into a syrup as in sodas.

The other part of the puzzle is that glycemic index doesn't measure insulin response: Fructose will trigger an insulin response, but insulin doesn't do much with fructose. The effect can desaturate the serotonin receptors in the gut and various other metabolic responses. What sugars, with what, can matter a great deal.

So the usual advice for diet goes: "Eat a good variety. Mostly plants. And not too much."

"Leaching" would be just your body running, assuming it has the full input it needs, getting the raw calories and giving the metabolic processes the full go-ahread, without actually having anything but the actual energy content to go on.

So yeah, eating an all-white diet could do that.

As far as alertness, my optimum combination is coffee relatively early, brief exercise to get my heart rate up, then working, while eating a diet of small meals, mixed vegetables and some starches. (Brown rice or whole-grain bread) -- six small meals a day works better for me than three larger ones, by far.

Re: Adenosine Normality

Good question. I haven't tried it, so I don't know. I suspect it's somewhere in between.

Edit: I may have mistaken your question earlier. What I do is indeed 'cycling', except that even when I do take caffeine, my quantity of consumption, and the consequent tolerance, is very low. So my experience has been that I pretty much experience a reset after a few days of abstinence, but that's a subjective feeling, of course.

If a heavy coffee drinker tried cycling, I don't know what would happen.